I"ve only been to BGW, but from the looks of BGT I would stick with BGW. When I'm at BGW, I don't feel like I'm in an amusement park, I feel like I'm truly in a getaway. the atmosphere is less ride/thrill oriented and more towards fitting in with a theme. The rides blend in, all being custom terrain rides, unlike the stock models BGT has. And the area around BGW is beautiful. Climbing the lift of Apollo's Chariot, all I see are the lush forests of the Williamsburg area, at BGT it sounds a lot more like its in an Urban/Suburban area.
Just my opinion, so don't shout at me BGT fanboys...